An internal combustion engine in a vehicle typically is in fluid communication with an air induction system and an air exhaust system for providing air to the engine, and exhausting air from the engine, respectively. In the internal combustion engine, sound energy is often generated in the form of acoustic pressure waves as air flows through the air induction and exhaust systems. In particular, vibrations are often caused by intake air flowing through an air feed conduit of the air induction system. Specifically, vibrations are caused by the induction of air into a cylinder of the internal combustion engine by a cyclic movement of a piston slidably disposed in the cylinder.
Generally, resonators are employed to reduce engine intake noise and improve noise comfort in the vehicle interior. Resonators operate by reflecting sound waves generated by the engine 180 degrees out of phase. The combination of the sound waves generated by the engine with the out of phase sound waves results in a reduction or cancellation of the amplitude of the sound waves. The air induction system in a four-cylinder vehicle, for example, typically requires a low frequency resonator (i.e. less than 250 hertz) or a quarter-wave resonator to attenuate the sound energy. Presently known low frequency and quarter-wave resonators, however, are required to be large in size in order to operate as desired. For example, a Helmholtz resonator may require a package volume of 6.0 liters and a quarter-wave resonator may have a length of 1.5 meters. In turn, such resonators are difficult to package and require complex routing to properly mount in an engine compartment. Additionally, manufacturing such large resonators requires expensive molding presses or additional processes for welding together multiple components of the resonators.
It would be desirable to produce a resonator which is readily configurable to attenuate low frequencies, wherein a structural complexity and a package size thereof are minimized.